subject: Carbon Fiber Fabrication - Infusion Technique [print this page] So you are interested in carbon fiber parts for your motorcycle, RC vehicle, automobile or something else. You have decided that you want to learn to make some carbon fiber parts yourself and so you are interested in learning about the different techniques. In this article we will describe the main techniques available and will concentrate on the epoxy infusion method.
The first technique of three that we will discuss will be what is referred to as pre-preg. This is carbon fiber fabric that is pre-impregnated with the precise amount of epoxy resin needed to make a strong and lightweight part. It requires the use of vacuum bagging and special ovens to cure the resin that other methods don't need. The fabric is very expensive and this combined with the need for other special equipment like the oven translates to very host costs. The quality is also very high and this method ranks about average for the time required to make each part.
The other common method for making carbon fiber is the wet layup technique. In this method layers of carbon fiber fabric are put down on a mold and wetted with freshly mixed resin by hand. Each layer is allowed to setup until tacky but not hard and another layer is laid on top until the desired thickness is achieved. There is no vacuum bagging and no ovens required and it utilizes inexpensive dry carbon fiber fabric so this method is very inexpensive. It does take some time as each layer has to setup for an hour or two so it high on the time factor. And while you can make a high quality part with this technique, its very easy to add too much or too little resin to the fabric and therefore hurt the quality of the final part. So its cheap, the quality can be good, but it takes some time.
Epoxy infusion is a slightly different process that does not require an oven or pre-preg material so costs are low. Instead, like wet lay up, it only uses dry fabric. And unlike wet lay up, all the layers of the part are made at the same time so it is much faster to make a part. The technique starts with a mold like any other method but in this case all the layers of dry fabric are stacked on top of the mold with no resin. The mold and fabric is then placed inside a vacuum bag and all the air is pumped out. Now the bag is pressed tightly against the fabric which is tightly pressed against the mold for a very good fit. Through an airtight coupling in the plastic bag a hose is attached with the opposite end placed in a container of resin. The vacuum inside the bag then draws the resin into the mold and infuses the dry fabric. Because of the constant pressure on the bag, the ratio of resin to fabric is tightly controlled and results is a very high quality, consistent part. Since there is no oven or pre-preg the costs are low and since all the layers are made at one time, the time it takes to make the part is low too.
Now you have it. You now know the major differences of the three most popular techniques for making carbon fiber. Pre-preg is of course the best but the costs are so high that it is way about the average hobbyist budget. Epoxy infusion seems to be the best balance of our three factors of cost, time, and quality. Yes you do have to purchase a vacuum pump and the related hoses, couplings, and plastics but these costs are a mere fraction of the costs involved in pre-preg production.
